The invention relates to a brake actuator, particularly for a rail vehicle brake.
Currently, three types of wheel braking systems are essentially used in the rail vehicle field: Pneumatic or electro-pneumatic braking systems, hydraulic or electro-hydraulic braking systems as well as mechanical or electromechanical braking systems. The wheel braking system may be constructed as an active or passive braking system, depending on whether the power of the brake actuator has to be applied for the engaging (active braking system) or for the releasing of the brake (passive braking system). In case of operating disturbances, energy is stored in air brake reservoirs if pneumatic systems are used; energy is stored in hydraulic reservoirs if hydraulic systems are used; and energy is accumulated in the form of accumulator-type springs when electromechanical systems are used.
From the prior art, electromechanical rail vehicle brakes are known which have a service-type brake unit as well as an accumulator-type brake unit which has an energy accumulator. The service-type brake unit contains a braking power generator for the application and/or release of the brake; for example, in the form of an electric-motor drive. The accumulator-type brake unit comprises at least one energy accumulator for the storage and supply of energy for the application of the brake as a service-type emergency brake when the service-type brake unit fails, and/or as a parking brake. The accumulator-type brake unit is generally constructed as a spring-loaded brake. A power converter provides a conversion of the energy supplied by the braking power generator and/or by the energy accumulator to a brake application movement and comprises, for example, a brake spindle driven by the electric-motor drive.
When the spring-loaded brake is triggered in the event of a parking braking or an emergency braking, the potential energy stored in the accumulator-type spring is abruptly released and is converted to high kinetic energy of the elements of the power converter which, after the braking position has been reached, are also abruptly decelerated. In this case, the braking system is subjected to high forces which may result in premature wear or damage.
In view of the above, the present invention is based on a brake actuator which, when the accumulator-type brake unit is triggered, lower loads will occur, while the braking effect is simultaneously high. Furthermore, this object is to be connected with lower constructional costs and should be able to be implemented in a space-saving manner.
Because the potential energy abruptly released when the accumulator-type brake is triggered is, for the most part, converted to rotational energy of the inertia weight, the remaining kinetic energy, by means which the elements of the power converter can be accelerated in the brake application direction, is reduced. For this reason, the shock load acting upon the braking system is reduced, whereby its service life and reliability is increased. The inertia weight is provided in addition to possibly already existing rotational bodies used exclusively for locking the accumulator-type brake unit. The rotational bodies also rotate after the release of the locking device. In particular, the inertia weight has a mass moment of inertia which is sufficient for a noticeable damping of the release of energy abruptly occurring during the release of the locking device. In comparison to linearly moving inertia weights, which require a relatively long acceleration path for generating a significant energy dissipation, less space is required for rotatory inertia weights. In addition, in contrast to oil-pressure-type or gas-pressure-type shock absorbers, the rotational inertia weight can be used independent of the temperature.
According to a particularly preferred arrangement, the forces and/or torques generated by the energy accumulator, when the locking device is locked, can be introduced at least by a portion of the inertia weight into a housing of the brake actuator and can be supported there. As a result, the inertia weight forms a component of the locking device and is integrated into its flux of force. The inertia weight therefore has a double function in that, in addition to reducing excess energy, it simultaneously acts as a locking element, whereby a particularly space-saving and light construction is obtained.
According to a further development, a transmission gearing with a preferably large gear ratio is arranged between the energy accumulator and the inertia weight. As a result, the forces are reduced which have to be applied for locking the inertia weight, which is simultaneously used as a locking element, in the release position. When the inertia weight is locked, for example, by electromagnetic holding forces, solenoid coils of a lower magnetic force are sufficient, whereby the current consumption and the heating-up of the brake actuator are reduced. Simultaneously, because of the large ratio, the rotational speed of the inertia weight is increased which is entered in a squared manner into the rotational energy, so that a high degree of damping will exist when the accumulator-type brake unit is triggered.
The inertia weight is expediently releasably coupled with the energy accumulator by a slipping clutch which is designed such that, after the braking position has been reached, the inertia weight is uncoupled from the energy accumulator. If the inertia weight and the bearing frictions are designed such that the inertia weight continues to rotate after the braking position has been reached, as a result of this arrangement, a gradual reduction of the rotational energy stored in it can take place, which has a positive effect on the service life of the brake actuator.
These and other aspects of the present invention will become apparent from the following detailed description of the invention, when considered in conjunction with accompanying drawings.